A three dimensional printer, i.e., an apparatus for 3D printing, can be considered as a robot carrying a material dispenser. Various competing 3D printing technologies exist; the 3D printing technology most relevant to the invention disclosed herein is described in U.S. Pat. No. 5,204,055 granted to Sachs, et. al, incorporated herein in its entirety. In this technique, a stream of fluid is directed towards a granular substrate. The combination of fluid and granular material solidifies into a solid article by either solvent action or chemical reaction engendered by the mixing of the two substances.
In the most commonly practiced version of this method, the fluid is dispensed by an ink-jet printhead that travels over the surface of a level bed of loose powder. This method provides a high degree of accuracy in the printed layers, and in the resulting article. Ink-jet printheads are capable of creating images from very uniform, tiny drops of fluid that are accurately placed. A fine grain of powder presents a substrate that can be assembled on a fine scale, and a degree of capillary attraction that holds the fluid in dense, tightly bonded features. One further benefit to using high-resolution ink-jets is the number of printing elements that can be grouped into an array is very large. This permits the machines using them to build solid objects at a speed much higher than other methods that use a single tool for forming material, such as an extrusion head or a laser beam.
Modern microfabrication techniques are facile at creating the intricate, tiny structures needed in ink-jet printheads. Durable materials can be used, and certain types of ink-jet printheads last for years if kept clean. Keeping the ink-jet printhead clean may be a challenge in an environment including the powder typically used for 3D printing.